Measurements of emissions from stacks are required to fulfil regulatory requirements, European Air Quality Directives and UK obligations under international treaties such as the Kyoto Agreement. Accurate, traceable measurements of flow in stacks underpins emissions monitoring and enables industry to report reliably against emission limit authorisations. Flow measurements are also important in developing an emissions trading strategy.

Who's Involved?

The project is funded as part of a consortium involving:

• The National Physical Laboratory (NPL), as lead contractor
• Source Testing Association (STA)
• Littlebrook Calibration and Manufacturing (LCM)

Background

NPL's considerable knowledge of stack emissions monitoring is being complemented by the STA, who represent the UK's stack emissions monitoring community. The STA's membership includes process operators, regulatory authorities and equipment manufacturers, therefore providing a considerable pool of knowledge and understanding of the issues associated with stack emissions monitoring from a range of perspectives. LCM is currently the only laboratory in the UK with UKAS accreditation for air velocity measurements using Pitot tubes and anemometers. They have an extensive understanding of the metrological aspects of flow measurement in this field.

Work Programme

The first phase of the project involved a comprehensive review of the key measurement issues in industrial emissions monitoring. This has included a survey of all members of the STA, followed by targeted telephone interviews. This established a baseline understanding of the range of flow measurements being carried out and the techniques being used. A review of previous validation work has also been carried out. The second phase of the project expanded on the measurement issues identified and defined a number of future work programmes.

The principle technique used to measure flow in stacks is the Pitot tube and a number of International Standards define methods for their application. However, it is increasingly evident that some of the fundamental assumptions underpinning the use of Pitot tubes are invalid under certain stack measurement conditions, potentially leading to significant measurement failures. A focus of this project has therefore been to review current knowledge and understanding of the issues in the use of Pitot tubes. In addition, a number of other flow measurement techniques used in stack monitoring, including dry gas volume metering and alternative in stack flow monitoring systems have been addressed.

Initial results of this work were presented at CEM2004, the 6th International Conference on Emissions Monitoring, 9-11 June, Milan. The paper presented at this conference is available here, CEM2004 Presentation ( PDF 172 KB)

For further information about the project ,please contact Rod Robinson